Abstract 3329: Correlation of Infarct Structure and Electrophysiologic Properties by Comparison of Delayed Enhanced Magnetic Resonance Imaging and Electroanatomic Mapping in Patients with Postinfarction Ventricular Tachycardia
Delayed enhanced magnetic resonance imaging (DEMRI) has been used to define the extent and volume of infarcted myocardium in patients with prior myocardial infarction. Electroanatomic mapping (EM) has also been used to identify the endocardial extent of post-infarction scarring. The purpose of our study was to gain insight into the infarct architecture and size as defined by DEMRI and its relation to characteristics of endomyocardial bipolar electrograms.
Methods: Six consecutive patients (5 men, mean age 69±10 years; EF:0.36±0.1) underwent DEMRI (1.5 Tesla, GE) prior to ablation and mapping of ventricular tachycardia. Using a 3-D EM system (CARTO, Biosense Webster; 4mm tip electrode) an EM was performed during sinus rhythm. A total of 2026 endocardial sites were analyzed. The electrograms (EGM) at these sites were categorized as normal (amplitude >3mV, width <70ms), fragmented EGMs (amplitude <0.5mV, width >133ms), isolated potentials (IP; potentials separated by an isoelectric segment >20ms from the ventricular EGM) or abnormal (remainder of EGMs). The DEMRI pictures were integrated into the electroanatomic map by customized segmentation of the left ventricle using anatomic reference points. Correlation of EM sites with respect to DEMRI was performed post hoc. Infarct size as defined by the extent of subendocardial delayed enhancement (DE) in the MRI correlated best with a voltage <1.0mV as compared to other cut-off values (R=0.92; P=0.02). Normal electrograms were exclusively found in areas without DE; 40% of the sites with abnormal EGMs were located in an area with DE; 80% of fragmented EGMs and 97% of sites with IPs were located in areas with DE. Sites with DE had a lower bipolar voltage (0.57±0.6mV vs 2.0±1.7mV; p<0.0001) and broader EGMs ( 117±60ms vs 78±13ms; p<0.0001) as compared to sites without DE.
Conclusion: DEMRI and EM are complementary techniques that can be combined. DEMRI helps to better define the infarct architecture and may help to facilitate mapping and ablation of postinfarction VT.